Magnetic write device with a cladded write assist element

ABSTRACT

A magnetic device includes a write element having a write element tip and a conductor adjacent an edge of the write element tip for carrying current to generate an assist field that augments a write field generated by the write element. A cladding material is disposed on at least one surface of the conductor.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.11/820,689, filed on Jun. 20, 2007.

BACKGROUND

The present invention relates to magnetic devices. More particularly,the present invention relates to a magnetic device that employs acurrent-carrying conductor to provide a magnetic field that assists awrite field.

As magnetic recording storage densities continue to progress in aneffort to increase the storage capacity of magnetic storage devices,magnetic transition (i.e., bit) dimensions and critical features of therecording device are being pushed below 100 nm. In addition, making therecording medium stable at higher areal densities requires magneticallyharder (i.e., high coercivity) storage medium materials. A magneticallyharder medium may be written to by increasing the saturationmagnetization value of the magnetic material of the recording device toincrease the magnetic field applied to the magnetic medium. However, therate of increase of the saturation magnetization value is not sufficientto sustain the annual growth rate of bit areal densities.

Another approach to overcoming the coercivity of a magnetically hardmedium is to provide a stronger write field by incorporating a writeassist device adjacent to the tip of the write pole that produces amagnetic field to reduce the coercivity of the magnetic medium near thewrite pole. This allows data to be written to the high coercivity mediumwith a lower magnetic field from the write pole. In addition, the fieldgradient around the write pole tip is improved due to cancellation ofstray fields from the write pole in regions that the assisting fieldopposes the write field. However, the regions in which the assist fieldopposes the write field are generally a distance from the write poletip, and thus the gradient improvement is limited in the region in whichtransitions are written to the magnetic medium.

SUMMARY

The present invention relates to a magnetic device including a writeelement having a write element tip and a conductor adjacent an edge ofthe write element tip for carrying current to generate an assist fieldthat augments a write field generated by the write element. A claddingmaterial is disposed on at least one surface of the conductor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is cross-section view of a magnetic writer including a trailingshield and a write assist conductor proximate a leading side of thewrite pole.

FIG. 2 is a graph of the perpendicular component of the net magneticfield as a function of the down-track position of the magnetic writerwith and without the write-assist conductor.

FIG. 3 is a cross-section view of a magnetic writer including a writeassist conductor proximate the trailing side of the write pole and aconductive coil portion proximate the leading side of the write pole.

FIG. 4 is a cross-section view of a magnetic writer including a writeassist conductor proximate the trailing side of the write pole and arecessed conductive coil portion proximate the leading side of the writepole.

FIG. 5 is a cross-section view of a magnetic writer including a writeassist conductor proximate the trailing side of the write pole, aconductive coil portion proximate the leading side of the write pole,and a single turn of conductive coil around the write pole.

FIG. 6 is a cross-section view of a magnetic writer including a writeassist conductor proximate the trailing side of the write pole, aconductive coil portion proximate the leading side of the write pole,and a half turn of conductive coil around the write pole.

FIG. 7 is a cross-section view of a magnetic writer including a writeassist conductor proximate the trailing side of the write pole, aconductive coil portion proximate the leading side of the write pole,and one and a half turns of conductive coil around the write pole.

FIG. 8 is a medium confronting surface view of the conductor proximatethe trailing side of the write pole tip and including a cladding layer.

FIG. 9A is a graph showing the perpendicular field component of magneticwriters with a cladded write assist conductor and with an uncladdedwrite assist conductor.

FIG. 9B is a graph showing the field gradient of magnetic writers with acladded write assist conductor and with an uncladded write assistconductor.

DETAILED DESCRIPTION

FIG. 1 is a cross-section view of magnetic writer 10, which includeswrite pole or element 12, current carrying conductor 14, first returnpole or element 16, second return pole or element 18, and conductivecoil 20. Write pole 12 is magnetically coupled to first return pole 16by first magnetic stud 24, and to second return pole 18 by secondmagnetic stud 26. Conductive coil 20 surrounds write pole or element 12such that portions of conductive coil 20 are disposed between write pole12 and first return pole 16, and between write pole 12 and second returnpole 18. Write pole 12 includes yoke 30 and write pole body 32 havingwrite pole tip 34. Shield 36 extends from second return pole 18 towardwrite pole tip 34.

First return pole 16, second return pole 18, first magnetic stud 24, andsecond magnetic stud 26 may comprise soft magnetic materials, such asNiFe. Conductive coil 20 may comprise a material with low electricalresistance, such as Cu. Write pole body 32 may comprise a high momentsoft magnetic material, such as CoFe, and yoke 34 and shield 36 maycomprise a soft magnetic material, such as NiFe, to improve theefficiency of flux delivery to write pole body 32.

Magnetic writer 10 confronts magnetic medium 40 at medium confrontingsurface 42 defined by write pole tip 34, first return pole 16, andsecond return pole 18. Magnetic medium 40 includes substrate 44, softunderlayer (SUL) 46, and medium layer 48. SUL 46 is disposed betweensubstrate 44 and medium layer 48. Magnetic medium 40 is positionedproximate to magnetic writer 10 such that the surface of medium layer 48opposite SUL 46 faces write pole 12. Magnetic medium 40 is shown merelyfor purposes of illustration, and may be any type of medium usable inconjunction with magnetic writer 10, such as composite media,continuous/granular coupled (CGC) media, discrete track media, andbit-patterned media.

Magnetic writer 10 is carried over the surface of magnetic medium 40,which is moved relative to magnetic writer 10 as indicated by arrow Asuch that write pole 12 trails first return pole 16, leads second returnpole 18, and is used to physically write data to magnetic medium 40. Inorder to write data to magnetic medium 40, a current is caused to flowthrough conductive coil 20. The magnetomotive force in conductive coil20 causes magnetic flux to travel from write pole tip 34 perpendicularlythrough medium layer 48, across SUL 46, and through first return pole 16and first magnetic stud 24 to provide a first closed magnetic flux path.The direction of the write field at the medium confronting surface ofwrite pole tip 34, which is related to the state of the data written tomagnetic medium 40, is controllable based on the direction that thefirst current flows through first conductive coil 20.

Stray magnetic fields from outside sources, such as a voice coil motorassociated with actuation of magnetic writer 10 relative to magneticmedium 40, may enter SUL 46. Due to the closed magnetic path betweenwrite pole 12 and first return pole 16, these stray fields may be drawninto magnetic writer 10 by first return pole 16. In order to reduce oreliminate these stray fields, second return pole 18 is connected towrite pole 12 via second magnetic stud 26 to provide a flux path for thestray magnetic fields. The stray fields enter first return pole 16,travels through first magnetic stud 24 and second magnetic stud 26, andexits magnetic writer 10 via second return pole 18.

Magnetic writer 10 is shown merely for purposes of illustrating anexample construction that may be used in conjunction with the principlesof the present invention, and variations on the design may be made. Forexample, while write pole 12 includes write pole body 32 and yoke 30,write pole 12 can also be comprised of a single layer of magneticmaterial. In addition, a single trailing return pole 18 may be providedinstead of the shown dual return pole writer configuration. Furthermore,second return pole 18 may be removed and shield 36 may “float” proximatethe trailing edge of write pole tip 34. These design variations are alsoapplicable to any of the magnetic writer configurations describedherein.

To write data to high coercivity medium layer 48, a stronger write fieldmay be provided to impress magnetization reversal in the medium. Toaccomplish this, conductor 14 is provided proximate to magnetic medium40 and the leading side of write pole tip 34. When a current is appliedto conductor 14, an assist magnetic field is generated that augments thewrite field produced by write pole 12. The combination of the writefield and the assist field generated by conductor 14 overcomes the highcoercivity of medium layer 48 to permit controlled writing of data tomagnetic medium 40. In addition, conductor 14 improves the write fieldgradient, which provides for a stronger write field proximate to writepole tip 34.

Conductor 14 may be formed from a portion of conductive coil 20 thatextends proximate medium confronting surface 42, or conductor 14 may bea conductive wire formed separately from conductive coil 20. Conductor14 may also have a cross-section that is smaller than that of conductivecoil 20, as is shown. In addition, conductor 14 may be connected inseries with conductive coil 20 such that the same current is suppliedthrough conductive coil 20 and conductor 14. In this configuration, onlyone preamplifier is required, and the overall power consumption ofmagnetic writer 10 may be reduced. A circuit may also be provided inseries with conductor 14 and conductive coil 20 such that the currentwaveform of the current through conductor 14 is ahead of or delayed withrespect to the current waveform of the current through conductive coil20. Conductor 14 may alternatively be connected in parallel withconductive coil 20 such that conductor 14 and conductive coil 20 aredriven by separate preamplifiers from the same current source. Conductor14 and conductive coil 20 may also be independently connected toseparate current sources.

Shield 36 is included in magnetic writer 10 to improve the down-trackwrite field gradient of magnetic flux from write pole 12. Magnetic fluxthrough write pole 12 that is induced by current through conductive coil22 passes through shield 36 parallel to magnetic medium 40. This reducesthe perpendicular field component in the region between shield 36 andmagnetic medium 40, providing most of the perpendicular component frommagnetic writer 10 proximate to write pole 12. As a result, informationrecorded in medium layer 48 is subject to less destabilization in thedown-track direction from magnetic writer 10.

Conductor 14 is disposed on a leading side of write pole tip 34. In someembodiments, conductor 14 is spaced less than about 100 nm from writepole tip 34. Conductor 14 may have a larger cross-section on the leadingside of write pole tip than if on the trailing side of write pole tip34, since the proximity of shield 36 to write pole tip 34 limits theavailable space on the trailing side of write pole tip 34. Consequently,the current density through conductor 14 is reduced relative to atrailing side conductor having a smaller cross-section, which reducesthe power consumption of magnetic writer 10. In addition, when conductor14 is disposed on the trailing side of write pole tip 34, theinteraction between the magnetic fields generated by conductor 14 andthe soft magnetic material of shield 36 may produce magnetic fieldslarge enough to partially erase data stored in medium layer 48. Bypositioning conductor 14 on the leading side of write pole tip 34, thistype of interaction is avoided.

Conductive coil 20 is recessed from medium confronting surface 42 bycoil recess CR, and write pole 12 has a core length CL that extends frommedium confronting surface 42 to magnetic studs 24 and 26. Coil recessCR and core length CL may be adjusted to provide variations inparameters related to the write field generated by magnetic writer 10.In some embodiments, coil recess CR and core length CL are minimized inlight of stray field considerations to increase the peak field generatedby magnetic writer 10 and/or reduce the rise time of the peak magneticfield when conductive coil 20 is energized. A reduction in rise timecorrelates to an increase in the data rate of magnetic writer 10.

To test the effect of adjusting coil recess CR, a 40 mA step coilcurrent with a rise time of 0.25 ns was applied to magnetic writer 10,and coil recess CR was varied while keeping all other dimensionssubstantially the same. In magnetic writer 10 with coil recess CR of 5.0μm and core length CL of 8.4 μm, the peak field was 11.3 kOe and therise time (i.e., the time to transition from 0% to 90% of the peakfield) was 0.6 ns. In magnetic writer 10 with coil recess CR of 1.0 μmand core length CL of 8.4 μm, the peak field was 11.6 kOe and the risetime was 0.4 ns. Thus, the coil recess CR may be reduced to improve thepeak field and rise time of magnetic writer 10.

To test the effect of adjusting core length CL, a 40 mA step coilcurrent with a rise time of 0.25 ns was applied to magnetic writer 10,and core length CL was varied while keeping all other dimensionssubstantially the same. In magnetic writer 10 with core length CL of 8.4μm and a coil recess of 1.0 μm, the peak field was 12.3 kOe and the risetime was 0.41 ns. In magnetic writer 10 with core length CL of 4.8 μmand coil recess CR of 1.0 μm, the peak field was 12.3 kOe and the risetime was 0.39 ns. Thus, the core length CL may also be reduced toimprove the rise time of magnetic writer 10.

FIG. 2 is a graph of the perpendicular component of the net magneticfield of magnetic writer 10 (write field from write pole 12 plus assistfield from conductor 14) as a function of the down-track position. Thenet magnetic field at the leading edge of write pole tip 34 is plottedat position 0.0, with down-track positions in the positive directionmoving toward the trailing edge of write pole tip 34. Line 60 shows thenet magnetic field of magnetic writer 10 as shown in FIG. 1 includingconductor 14 at the leading side of write pole tip 34, while line 62shows the net magnetic field of magnetic writer 10 without conductor 14at the leading edge. For line 60, conductor 14 was positioned about 50nm from write pole tip 34, had cross-section dimensions of 200 nm by 200nm, and was driven by a 10 mA current. As is shown, the net magneticfield from magnetic writer 10 increased by approximately 8% whenconductor 14 was included at the leading edge of write pole tip 34,while maintaining a good field gradient.

Other parameters related to magnetic writer 10 may also be varied toimprove the efficiency of magnetic writer 10. For example, FIG. 3 is across-section view of magnetic writer 70 including conductor 14proximate the trailing side of the write pole and a portion 20 a ofconductive coil 20 proximate the leading side of write pole tip 34. Inthis embodiment, conductive coil 20 includes two turns that surroundwrite pole 12. By reducing the number of turns in conductive coil 20,the efficiency of magnetic writer 70 is improved and the power consumedby magnetic writer 70 is reduced. In addition, core length CL and coilrecess CR of magnetic writer 70 is reduced compared to magnetic writer10 to improve the rise time and peak field generated. By reducing corelength CL, coil recess CR, and the number of turns of conductive coil 20around write pole 12, the amount of flux leakage and side track erasurefrom magnetic writer 70 is also reduced.

Conductive coil portion 20 a is a quarter turn of conductive coil 20disposed proximate medium confronting surface 42. Conductive coilportion 20 a may have a cross-section that is substantially equal to orlarger than the cross-section of conductor 14. In addition, thecross-section of conductive coil portion 20 a may be substantially equalto or smaller than the cross-section of the remainder of conductive coil20. Conductor 14 may be connected in series or in parallel withconductive coil 20 and conductive coil portion 20 a. Conductor 14 mayalternatively be another quarter turn of conductive coil 20 disposed onthe leading side of write pole tip 34.

When conductive coil 20 and conductive coil portion 20 a are driven by acurrent, the magnetomotive force in conductive coil 20 induces themagnetic flux from write pole tip 34 to produce the write field. Amagnetic field is also generated by conductive coil portion 20 a thataugments the write field produced by write pole 12. Furthermore,conductor 14 is provided proximate magnetic medium 40 at the trailingside of write pole tip 34. When a current is applied to conductor 14, anassist magnetic field is generated that further augments the write fieldproduced by write pole 12. The combination of the write field, the fieldgenerated by conductive coil portion 20 a, and the assist fieldgenerated by conductor 14 provides an increase in the net field atmagnetic medium 40 (FIG. 1) to overcome the high coercivity of mediumlayer 48 and permit controlled writing of data to magnetic medium 40.Because the net field generated by magnetic writer 70 is increased withthe inclusion of conductive coil portion 20 a, the efficiency ofmagnetic writer 70 is improved, which allows for a reduction in thecurrent applied to conductive coil 20.

FIGS. 4-7 show various other representative magnetic writerconfigurations that provide improved efficiency, reduced powerconsumption, improved rise time and peak field, and/or reduced fluxleakage and side track erasure. FIG. 4 is a cross-section view ofmagnetic writer 80 including conductor 14 proximate the trailing side ofwrite pole tip 34 and conductive coil portion 20 a proximate the leadingside of write pole tip 34. In this embodiment, conductive coil 20includes a single turn that surrounds write pole 12. A smaller number ofturns in conductive coil 20 improves the efficiency of magnetic writer80, and the power consumed by magnetic writer 80 is reduced. Inaddition, the rise time and peak field generated by magnetic writer 80is improved due to a smaller core length and coil recess. By reducingthe core length, the coil recess, and the number of turns of conductivecoil 20 around write pole 12, the amount of flux leakage and side trackerasure from magnetic writer 80 is also reduced.

The cross-section of conductive coil 20 is increased to allow for theapplication of a larger write current and reduce the stray fields fromconductive coil 20. In addition, half-turns of conductive coil 20 areoffset with respect to each other relative to the longitudinal dimensionof write pole 12 to adjust the flux profile in write pole 12. Conductivecoil portion 20 a is recessed from medium confronting surface 42 and hasa cross-section smaller than the remainder of conductive coil 20 andlarger than conductor 14 to provide a controllable field from conductivecoil portion 20 a at magnetic medium 40. Conductive coil portion 20 a isalso disposed a distance from the leading edge of write pole tip 34 topermit fields from conductive coil portion 20 a to be focused by yoke30.

FIG. 5 is a cross-section view of magnetic writer 90 including conductor14 proximate the trailing side of write pole tip 34 and conductive coilportion 20 a adjacent the leading side of write pole tip 34. In thisembodiment, conductive coil 20 includes a single turn that surroundswrite pole 12 such that half-turns of conductive coil 20 aresymmetrically disposed with respect to the longitudinal dimension ofwrite pole 12. A smaller number of turns in conductive coil 20 improvesthe efficiency of magnetic writer 90, and the power consumed by magneticwriter 90 is reduced. In addition, the rise time and peak fieldgenerated by magnetic writer 90 is improved due to a smaller core lengthand coil recess. By reducing the core length, the coil recess, and thenumber of turns of conductive coil 20 around write pole 12, the amountof flux leakage and side track erasure from magnetic writer 90 is alsoreduced.

Conductive coil portion 20 a is recessed from medium confronting surface42 and has a cross-section smaller than the remainder of conductive coil20 to provide a controllable field from conductive coil portion 20 a atmagnetic medium 40. Conductive coil portion 20 a is disposed proximatemedium confronting surface 42 to maximize the net field strength atmagnetic medium 40.

FIG. 6 is a cross-section view of magnetic writer 100 includingconductor 14 proximate the trailing side of write pole tip 34 andconductive coil portion 20 a adjacent the leading side of write pole tip34. In this embodiment, conductive coil 20 includes a half-turn aroundwrite pole 12. A smaller number of turns in conductive coil 20 improvesthe efficiency of magnetic writer 100, and the power consumed bymagnetic writer 100 is reduced. In addition, the rise time and peakfield generated by magnetic writer 100 is improved due to a smaller corelength and coil recess. By reducing the core length, the coil recess,and the number of turns of conductive coil 20 around write pole 12, theamount of flux leakage and side track erasure from magnetic writer 100is also reduced.

First magnetic stud 24 is extended to be more proximate mediumconfronting surface 42 than second magnetic stud 26 to provide a largerfeature to receive stray fields from outside sources. Conductive coilportion 20 a is positioned between yoke 30 and medium confrontingsurface 42 to maximize the net field strength at magnetic medium 40.Conductive coil portion 20 a has a cross-section smaller than theremainder of conductive coil 20 and larger than conductor 14 to providea controllable field from conductive coil portion 20 a at magneticmedium 40.

FIG. 7 is a cross-section view of magnetic writer 110 includingconductor 14 proximate the trailing side of write pole tip 34 andconductive coil portion 20 a adjacent the leading side of write pole tip34. In this embodiment, conductive coil 20 includes a one and a halfturns that surround write pole 12. This allows for a larger amount fluxdeveloped in write pole 12 compared to the embodiments shown in FIGS.4-6 due to the larger number of turns surrounding write pole 12. At thesame time, compared to the embodiments shown in FIGS. 1 and 3, thesmaller number of turns in conductive coil 20 improves the efficiency ofmagnetic writer 110 and the power consumed by magnetic writer 110 isreduced. In addition, the rise time and peak field generated by magneticwriter 110 is improved due to a smaller core length and coil recess. Byreducing the core length, the coil recess, and the number of turns ofconductive coil 20 around write pole 12, the amount of flux leakage andside track erasure from magnetic writer 110 is also reduced.

First magnetic stud 24 is extended to be more proximate mediumconfronting surface 42 than second magnetic stud 26 to provide a largerfeature to receive stray fields from outside sources. Half-turns ofconductive coil 20 are offset with respect to each other relative to thelongitudinal dimension of write pole 12 to adjust the flux profile inwrite pole 12. Conductive coil portion 20 a is positioned between yoke30 and medium confronting surface 42 to maximize the net field strengthat magnetic medium 40. Conductive coil portion 20 a has a cross-sectionsmaller than the remainder of conductive coil 20 and larger thanconductor 14 to provide a controllable field from conductive coilportion 20 a at magnetic medium 40.

FIG. 8 is a medium confronting surface view of conductor 14 includingcladding layer 120 disposed on a side of conductor 14 opposite writepole tip 34. Conductor 14 is positioned along the medium confrontingsurface adjacent to the trailing edge of pole tip 34. Alternatively,conductor 14 may be disposed adjacent a leading edge of pole tip 34(such as is shown in FIG. 1), with cladding layer 120 on a side oppositewrite pole tip 34. First electrical contact 122 a and second electricalcontact 122 b overlay portions of conductor 14 that extend beyond theedges of pole tip 34. The overlaid surfaces of electrical contacts 122 aand 122 b are very much larger than cross-section of conductor 14. In analternative embodiment, first electrical contact 122 a is electricallyconnected to one end of conductor 14 and second electrical contact 122 bis electrically connected to an opposite end of conductor 14. Electricalcontacts 122 a and 122 b are coupled to a current source (not shown),which provides a wire current I_(W) that flows through electricalcontacts 122 a and 122 b and conductor 14. Heat sink 126, which isseparated from cladding layer 120 and electrical contacts 122 a and 122b by insulating material 124, may be provided to allow for heat transferacross insulating material 124.

Current I_(W) generates the write assist field around conductor 14. Thedirection of current I_(W) determines the direction of the write assistfield that is generated around conductor 14 pursuant to the right-handrule. In order to provide a magnetic field that augments the write fieldproduced by write pole tip 34, current I_(W) is directed to generate awrite assist field that has the same orientation as the write field. Athigh current densities through conductor 14, there is a large enoughflux density generated in pole tip 34 such that the magnetization ofwrite pole tip 34 is driven to near saturation, beyond which theadditional field from conductor 14 augments the field from write poletip 34. This results in magnetic field amplification at magnetic medium40. In addition, the field profile from conductor 14 maps onto that ofwrite pole tip 34 so as to yield improved field gradients. Furthermore,fields at the trailing edge of conductor 14 cancel stray fields fromwrite pole tip 34, leading to a sharper down-track field profile.Conductor 14 and electrical contacts 122 a and 122 b are separated fromwrite pole tip 34 and cladding layer 120 by a thin layer of insulatingmaterial 124 to provide electrical isolation of these components whilemaintaining them in close proximity to each other. In addition, claddinglayer 120 is magnetically isolated from conductor 14.

Cladding layer 120 is comprised of a magnetic material and is providedon conductor 14 to focus the assist field from conductor 14 into atighter radius, thereby improving the field gradient and the gradientdecay of the magnetic writer. Cladding layer 120 may be incorporatedinto any of the magnetic writers described above to provide fieldgradient improvements. Cladding layer 120 serves to at least partiallybalance the field generated by conductor 14 on a side opposite writepole tip 34 with stray fields from write pole 12 (which have a directionopposite that of the local fields from conductor 14). The net fielddown-track from write pole tip 34 drops sharply due to the balancedfields to provide a high gradient. Cladding layer 120 may have across-track width (left to right in FIG. 8) less than that of conductor14 to provide control of the magnetic field profile in the cross-trackdimension. Cladding layer 120 may also have a cross-track widthsubstantially equal to that of conductor 14 to maximize the net fieldfrom the magnetic writer. Furthermore, while cladding layer 120 is shownproximate one external surface of conductor 14, cladding layer 120 mayalternatively be provided adjacent additional external surfaces ofconductor 14.

The gradient and gradient decay improve with increased applied currentsI_(W). In some embodiments, the field from write pole tip 34 and thefield from conductor 14 are controlled to provide a net field atcladding layer 120 of approximately zero. The field balance at claddinglayer 120 is a function of the current through conductive coil 20,current I_(W) through conductor 14, the dimensions of cladding layer120, and the dimensions of write pole 12. A simulation model showed thatthis balance can be achieved for media coercivity ranges of betweenabout 4,000 Oe and about 10,000 Oe with current densities of about 10⁸A/cm² to about 5×10⁸ A/cm².

FIG. 9A is a graph showing the perpendicular field component H_(perp) ofa magnetic writer with conductor 14 including cladding layer 120 (line130) and a magnetic writer with conductor 14 and no cladding layer 120(line 132). Both writers tested also included a conductive coil 20surrounding write pole 12 and were tested with optimum parameters foruse with magnetic medium 40 having a coercivity of 5,000 Oe. Conductivecoil 20 carried a 60 mA current, and conductor 14, which had across-track length of 200 nm and a down-track width of 50 nm, was drivenby a 15 mA current. The perpendicular magnetic fields at the leadingedge of write pole tip 34 is plotted at down-track position 0.0 μm, withdown-track positions in the positive direction moving toward thetrailing edge of write pole tip 34. Cladding layer 120 is located atdown-track position of about 0.2 μm for line 130. As is shown, claddinglayer 120 provides a sharp drop in the perpendicular field H_(perp) downtrack from write pole tip 34. In the device tested for line 130, thecurrent through conductive coil 20, the current through conductor 14,the dimensions of cladding layer 120, and the dimensions of write pole12 were such that the net magnetic field at cladding layer 120 wasapproximately zero.

FIG. 9B is a graph showing the gradient of the magnetic writer withconductor 14 including cladding layer 120 (line 140) and the magneticwriter with conductor 14 and no cladding layer 120 (line 142). Thegradient of each magnetic writer tested is plotted versus theperpendicular field H_(perp). As is shown, the field gradient for amagnetic writer including conductor 14 and cladding layer 120 (line 140)is greater and more uniformly distributed than the field gradient for amagnetic writer with conductor 14 and no cladding layer 120 (line 142).

In summary, the present invention relates to a magnetic device includinga write element having a write element tip and a conductor adjacent anedge of the write element tip for carrying current to generate an assistfield that augments a write field generated by the write element. Acladding material is disposed on at least one surface of the conductor.The cladding layer focuses the assist field from the conductor into atighter radius, thereby improving the field gradient and the gradientdecay of the magnetic writer.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

The invention claimed is:
 1. A magnetic device comprising: a writeelement including a write element tip; a return element magneticallycoupled to the write element; a write coil for carrying a current toinduce a write field in the write element; and a conductor positionedbetween the write element and the return element for carrying current togenerate an additional field that produces stray field cancellation in adown-track direction and a magnetic cladding material proximate at leastone surface of the conductor, wherein a cross-track width of thecladding material is substantially equal to or less than a cross-trackwidth of the conductor.
 2. The magnetic device of claim 1, wherein themagnetic cladding material is proximate a side of the conductor oppositethe write element tip.
 3. The magnetic device of claim 1 furthercomprising: a shield extending from the return element toward the writeelement tip.
 4. The magnetic device of claim 1, wherein the magneticcladding material is magnetically isolated from the write element. 5.The magnetic device of claim 1, wherein a cross-track width of thecladding material is less than a cross-track width of the conductor. 6.The magnetic writer of claim 1, wherein the conductor is a portion ofthe write coil.
 7. A magnetic writer comprising: a write element thatgenerates a write field at a front surface; a return elementmagnetically coupled to the write element; a write coil for carrying acurrent to induce the write field at the front surface; a conductorpositioned at the front surface between the write element and the returnelement for carrying current to generate a field; and a magneticcladding proximate a down-track surface of the conductor, wherein across-track width of the cladding material is substantially equal to orless than a cross-track width of the conductor.
 8. The magnetic writerof claim 7, wherein the magnetic cladding is on a side of the conductoropposite the write element.
 9. The magnetic writer of claim 7, andfurther comprising: a shield extending from the return element towardthe write element.
 10. The magnetic writer of claim 7, wherein thecladding is magnetically isolated from the write element.
 11. Themagnetic writer of claim 7, wherein a cross-track width of the claddingmaterial is less than a cross-track width of the conductor.
 12. Themagnetic writer of claim 7, wherein the conductor is a portion of thewrite coil.
 13. A device comprising: a write element including a writeelement tip; a return element magnetically coupled to the write element;a conductor positioned between the write element and the return elementfor carrying current to generate an additional field that cancels strayfield from the write element tip in a down-track direction, wherein across-track width of the conductor is substantially greater than across-track width of a cladding material proximate the conductor. 14.The device of claim 13, wherein a magnetic cladding material isproximate at least one surface of the conductor.
 15. The device of claim14, further comprising a write coil for carrying a current to induce awrite field in the write element.
 16. The device of claim 15, whereinthe conductor is positioned at the front surface between the writeelement and the return element.
 17. The device of claim 14, wherein themagnetic cladding material is between the conductor and the returnelement.
 18. The device of claim 14, wherein the magnetic claddingmaterial reduces the radial focus of an assist field from the conductor.19. The device of claim 14, wherein the magnetic cladding material ismagnetically isolated from the write element.
 20. The device of claim13, wherein a width of the cross-track width of the cladding material isless than a cross-track width of the conductor.